Water-heater construction.



F. L. 0. WADSWORTH. WATER HEATER CONSTRUCTION.

APPLICATION FILED JAN.25,1913. 1,131,021

Patented Mar. 9, 1915.

5 SHEETSSHEET 1.

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F. L. O. WADSWORTH. WATER HEATER CONSTRUCTION.

APPLICATION FILED JAN 25, 1913.

WITNESSES F. L. O. WADSWORTH. WATER HEATER CONSTRUCTION Patented Mar. 9,1915.

APPLICATION FILED JAN 25 1,1 31,021

5 SHEETS-SHEET 3.

INVENTDR 7 r Qa/ 'IIIIIII WITNESSES P. L. O. WADSWORTH. .WATER HEATERCONSTRUCTION.

Patented Mar. -9, 1915.

- 7 APPLICATION FILED JAN. 25, 1913. 1, 1 3 1 ,021

5 SHEETS-SHEET 4.

INVENTOR WITNESSES w F. L. 0. WADSWORTH.

WATER HEATER CONSTRUCTION.

APPLICATION FILED JAN.25, 1913.

Patented Mar. 9, 1915.

5 SHEETS-SHEET 5v INVENTOR y/M 4 WITNESSES UNITED STATES PATENT oFnroE;

FRANK I4. 0. WADSWORTH, OF SEWICKLEY, PENNSYLVANIA.

WATERr-HEATEB- CONSTRUCTION.

Specification of Letters Patent. Patented Mar, 9, 1915,

Application filed January 25, 1913. Serial No. 744,197.

To all whom it may concern Be it known that I, FRANK WORTH, a citizen ofthe United States, residin'g-at Sewickley, in the county of Alleghenyand State of Pennsylvania, have invented certain new and usefulImprovements in Water-Heater Construction, of which the following is aspecification.

My invention relates to water heater construction, particularly to thattype which is known as an instantaneous heater; but

certain features of my invention may also be applied to the constructionof heaters of the storage tank type. Some of the objects of my inventionare:First, to provide a construction in which the control of the fuelsupply is jointly effected by water actuated elements and bythermostatically actuated elements cooperating with each other toregulate a single port or valve opening through which the gas passes tothe main burners of the heater; second, to provide certain forms ofimproved thermostatic devices which are subject not only to the actionof the hot water in the heating receptacle or hot water flowingtherefrom, but also to the action of the cold liquid supplied from thewater main; third, to provide improved means for automatically shuttingoff the connection between the cold water inlet to the heater and thewater main as soon as the flow of water through the apparatus is stoppedand simultaneously opening a communication between the outlet and inletof the heating receptacle thereby establishing a path for the freecirculation of the water in the receptacle under the heating influenceof the pilot light or other burners; fourth, to providea very simple andcompact mechanism which can be constructed at small expense and whichwill be in large part contained in a single chamber or casing. Otherobjects andadvantages of my invention will appear from a perusal of thespecification, and inspec tion of the drawings which form a partthereof.

In thedrawings Figs. 1 and 2 illustrate in side and front elevationrespectively one form of heating apparatus of the so-calledinstantaneous type in connection with which my invention may be used.Fig. 3 illustrates in enlarged vertical cross-section the constructionof control mechanism used in the apparatus of Figs. land 2; Figs. 4 and5 are detail views showing parts of the mechanism of Figs. '1, 2 and 3;Fig. 6 is a vertical L. O. WADsi of ,the gas valve when the outletcross-sectional view through a second form of control mechanism alsoembodying my improvements; Figs. 7 and 8 are similar views of anotherembodiment of my invention; Fig. 9 is a detail view of a modification ofthe construction shown in Fig. 7; Fig. 10 is a vertical cross-sectionalelevation of still another'form' of my improved control mechanism; Figs.11 and 12 are detail views of certain parts of the construction of Fig.10; Fig. 13 illustrates in similar vertical crosssection anotherapparatus embodying certain features of my improvements; Figs. 14. and15 are vertical cross sectional views of mechanisms which-embody certainfeatures of my. invention that are especially adapted .for use inconnection with storage tank heaters; Figs. 16 and 18 are verticalsections through other modified forms of controlling mechanisms; andFig. 17' is a horizontal section through a structure very similar toFig. 16, but with an addition thereto, and at about the level indicatedby the line XVII-XVII.

Referring first to the general arrangement of the heater parts as shownin Figs. 1 and 2; A is the casing of the heater; B indicates the uppercoils of the heater; C is the lower reverse coil connected to the uppercoils by means of the pipe 1); E are the gas burners mounted upon theusual burner ring; F is Y the gas supply pipe G is the casing of the gasthe burners; H is the gas pipe leading from the gas valve to the ringwhich carries the burners E; I is the casing containing the thermostat;and K is the casing of the water actuated member for securing theoperation from the heater is opened and closed.

Referring now to Fig. 3 in conjunction with Figs. 1 and 2; 1 indicatesthe connection leading from thewater main to the control apparatus, 2indicates the cylinder containing the water actuated member into theupper end of whichthe pipe 1 leads, 3 indicates the water inlet leadingto the top coil 13 of the heating receptacle, 4 indicates the wateroutlet leading from the lower reverse coil C of said receptacle into thebottom of the chamber containing the thermostat, and 5 indicates the hotwater outlet leading from cated in the cylinder 2 is made in the form ofa packed piston having a central perfothe top of said chamber to thehouse system.

The water actuated member 6 whichis lorated boss 7. which is conedexteriorly to fit loosely within a reversely coned boss 8 on the topcylinder head and is provided at its center with a check valve 9normally held to its seat by a spring 10 interposed between the head ofthe check valve and a perforated disk 11 resting on the top of the pipe12. This pipe 12 leads downwardly from i the central opening in thepiston member 6 and terminates near the lower end. of a second pipe 13.In the lower end of the pipe 12 is secured a cap 14 which bears againstthe upper end of a stem 15 which passes down through a 'stufling box ina second cap 16 which closes the lower end. of the pipe 13. Both thelower end ofthe pipe 12 and the cap 14 are perforated with ports 17through which water can pass freely from the pipe 12 into the pipe 13.The latter pipe, as already stated, is closed at its lower end with acap 16 and is secured at its upper end to a head or collar 18 which ismounted in turn on. a third pipe 19 concentric with the two inner pipes12 and 13. The lower end of the pipe 19 is brazed to a screw collar 20which is mounted in the upper part of the casing G which contains thegas valve and portion of the control mechanism therefor. A fourth pipeT, concentric with the three inner ones is also secured in the topportion of this same casing and extends upwardly to a screw coupling 22on which a top casing K containing the water actuated member rests. Theupper portion 'of the casing G is also provided with a lateral port 23which leads to the hot water outlet 4. The top casing K is likewiseprovided with a port 24 which communicates at one end with the lower endof the cylinder 2, and at the other with the cold water inlet 3,, and isfurther provided with a second port 25 which establishes communicationbetween the upper end of the space between the two outer tubes 19 and Iand the hot water outlet 5 which leads to the house supply system. Aswill be readily seen the construction just described is such that thewater which flows past the check valve 9 into the upper end of the pipe12 is forced to pass down through the latter, then up again through theannular space between the pipes 12 and 13, thence into the lower end ofthe cylinder 2 and thence through the port 24 into the cold water inlet3. After passing through the heater coils the water emerges from the hotwater outlet 4, and enters the annular space between the two outer pipes19 and I, and passes upwardly and fiows through the port 25 into thesupply pipe 5. The two inner tubes 12 and 13 are made of iron, steel,Invar metal, or similar material having a low coefficient of expansion;and the two outer pipes 19 and I are made of brass, copper, or othersuitable material having a high coefficient of expansion; and the twosystems of pipes connected and arranged as above described constitute acomposite thermostat member of which the inner element'is subjected tothe cooling action. of the infiowing water, and of which the outerelement is subjected to the separate action of the outflowing water. Itwill be further noted that the outer pipe 13 of the innerthermostatmem-- her, and the inner pipe 19 of the outer thermostatmember are separated by a dead air space which thermally insulates thetwo members of the thermostat from each other. The lower end of the stem15 abuts against the closed upper end of a hollow piston element 26which slides vertically in the gas valve casing G and carries at itslower end a head 27 which projects inwardly to form a seat on which thegas valve 28 is normally held by gravity The piston 26 is perforatedwith a series of ports 29 which afford communication between theinterior of the cylinder and an external circular chamber 30 formed inthe gas valve casing and communicating with the gas inlet pipe F; The

lower end of the casing G is Closed y a Cap.

31 having a side opening 32 which communicates with the gas outlet pipeH leading to the main burners of the heater. The cap 16 which forms theterminal of the inner negative thermostat element is provided with twodownwardly extending studs 33 and 34 (see detail of Fig. 5) one justbehind, and one just in front of the sectional plane of Fig. 3. These'studs bear at their lower ends on a thermostat lever 35 which iscentrally perforated to allow the passage of the stem 15 and which bearsat its right hand end on a knife edge 36 supported on an extension ofthe side wall of the gas valve casing G. The long end of this thermostatlever 35 bears on a compression spring 37 by means of which thethermostat lever is kept in engagement with the studs 33 and 34 andknife edge 36. The outer end of said lever is also perforated to receivean end of a rod 38 which passes down through bearings in lateralextensions 39 and 40 from the wall of the gas valve casing G and bearsat its lower end on the short arm of a second thermostat lever 41. Thelong arm of this lever 41 is provided with an adjustable screw 42,adapted to engage with the lower end of the gas valve stem 43 whichpasses upward through a stuihng box in the cap 31 and enters a conedrecess at the center of the gas the rod 38 normally downward as far asthe engages with the adjacent shouldered end of the cylinder in whichsaid piston moves. In this position the water actuated member 6 is alsoraised to such a position that the end of the boss 8 engages with theadjacent face of the piston member and completely closes ofi'communication between the upper end of said cylinder and the pipe 12. Inorder to take care of any loss of motion which there may be-whetherintentionally provided in the original design or occurring later. asresult of wear between the ends of the stem 15 and the members 26 and 14with which they contact-a second compression spring 48.may be interposedbetween the two caps 14 and 16, but this spring may in some cases beomitted. When the piston member 6 is in its elevated position it bearsagainst an adjustable head 49 (suitably secured by a lock nut or similardevice) on the upper end of the stem 50 of a puppet valve 51, and raisesthe latter from its seat thereby opening the port of said puppet valveand estab lishing a communication between the upper end of the annularspace between the two outer thermostat members and the port 24 whichleads to the cold water inlet 3 of the heater. coils. The opening ofthis port allows the water to circulate freely, under the heatinginfluence of the pilot light or other burners, through the heater coilsbetween the inlet 3 and the outlet 4. In order to prevent accidentalrotation of the piston member 6which might bind the parts 50 and 51I mayprovide a guide stem 52, the lower end of which is secured to the bottomhead of the cylinder 2, and the upper end of which passes through a holein the piston member 6.

The. operation of this control mechanism in the practical use of theheater to which it is applied is as follows: When no water 1s flowingthrough the heater-except as the result of natural circulation throughthe coilsthe piston member 6 is in the position shown in the figure inwhich all communication between the supply pipe 1 and the rest of theapparatus is cut ofi. In this position the gas valve piston 26 is alsoin itshighest position, and the gas valve 28 is held against its seat,both by its own weight and by the pressure of the gas on its upper side,so that no fuel can pass through the gas'valve chamber into the fueloutlet pipe H which supplies the main burners of the heater. But as soonas water is withdrawn from the heating receptacle-as by opening a tapconnected with the house supply line 5-the pressure on the lower side ofthe piston member 6 is reduced byv such withdrawal of water, and thesuperior pressure on the top of the piston will force the latter downthereby opening the port between the reversely coned bosses 7 and 8 andallowing water to flow through this port and past the check valve 9 intothe pipe 12, andthence onthe path previously indicated to the inlet 3 atthe top coil. of the heater; The first downward movementof the pistonmember 6 closes the puppet valve 51, and thereby compels all water whichflows out of the pipe 5 to pass from the inlet 3 through the heatingcoils. The downward movement of the piston 6 further depresses the gasvalve piston 26 until the parts assume the position shown in Fig. 4where the cap 27 has been brought in contact with the upper end of thecap 31. In this position the ports 29 are full open, and the gas valve28 is raised from itsseat by the engagement of the upper end of the stem43 with the central coned recess of the gas valve head. By adjusting thescrews 42 and 44 I can vary the maximum opening of the gas valve port asdesired. Gas will now flow from the gas inlet pipe F through-the portopenings 29 and gas valve port to the gas outlet pipe H and thence on tothe main burners of the heater where it will be ignited by the usualpilot light, the connections for which are not shown in this drawing. Asthe temperature of the flowing water rises the outer member 19 of thethermostat will expand-the inner member 13 being kept cold by theinfiowing water and the expansion of said outer member will raise thecap 16 and the studs 33 and 34 connected thereto, thereby allowing thethermostat lever 35 to be carried upward by the spring 37 until it isbrought in contact with the adjustable head 53 on the upper end of therod 38., The spring 37 is considerably stronger than the spring 46whicl1is made just strong enough to support the weight of the gas valve head28-and when the thermostat lever 35 engages with the head 53 the tensionof the stronger spring 37 overcomes the tension of the weaker spring 46,and thereby lifts the rod 38 allowing the long arm of the second lever41 to fall and permitting the gas valve 28 to move downward toward itsseat. As shown in Figs. 3, 4, and

6 the gas valve is provided on'its lower side with a conical collarwhich enters a correof the gas valve port being'eflected solely by thecontact of. the flat leather face portion of the gas valve head with itsraised seat. This final contact-which determines the point at which thefuel supply to the main burners is completely out offcan be made to takeplace at any desired temperature of the outflowing water by theadjustment of the nut 53. The gas valve will remain closed until thefall in temperature of the outflowing water has caused the outer member19 of the thermostat to contract sufiiciently to carry the topthermostat lever 35 out of engagement with the head 53, whereupon therod 38 will be depressedby the action of the spring 46 thus once moreraising the gas valve from its seat and admitting another supply of fuelto the main burners. lhese successive opening and closing movements ofthe gas valve will continue as long as water continues to flow and torise above and fall below the point at which the thermostatic mechanism.may be set to cut ed the supply of fuel. But as soon as the flow ofwater is stopped the pressure on the two sides of the piston member 6will be at once equalized, and the latter will be raised by the actionof the springs 48 and t'L-or by the latter alone if the former is notused; and the resultant upward movement of the gas valve piston 26 willcarry the gas valve 28 up with it and out of engagement with thethermostat mechanism so that the latter can no longer act on the gasvalve until the flow of water has been again started and the gas valvepiston 26 thereby depressed to the position shown in Fig" 4:. If, whenthe-flow of water is stopped the piston member 6 should for any reasonhe stuck in its depressed or opened position no damage could result tothe heating apparatus because the thermostatic-mechanism would still goon acting to shut off the supply of gas whenever the water in the coilshad been raised to the point of thermostatic cut ofi. But the return ofthe piston to its normal position can be insured by the use of the checkvalve 9 which, as soon as the flow of water is stopped, is seated by thespring 10 and thus confines the body of liquid in the heater betweensaid check valve and the now closed house service pipe. Any furtherheating of this inclosed bodyof liquid immediately expands it and thisexpansion exerts a powerful back pressure on the lower side of thepiston member 6 thereby forcing the latter back to its initial positionand relieving the gas valve piston 26 from all restraining downwardpressure which could tend to hold it in the position of Fig. 4. Sincethis gas valve piston is packed as shown and may therefore be veryloosely fitted in its cylinder (the gas pressure being never normallymore than a few ounces at the most) there is no possibility whatever ofit being stuck in this position. In this upper position shown in'Fig, 3-any leakage past the piston to the fuel outlet pipe H is prevented bycontact of the flanged end of the cap 27 with the engaging shoulder(which may if desired be also provided with a leather face) of the gasvalve casing G.

In the construction shown in Fig. 6 the Water enters the apparatus fromthe house main through a pipe 1, which communicates as before with theupper end of a cylinder 2 containing the water actuated member 6. Theconstruction of this member 6' is in general similar to that of thecorresponding member shown in the construction of Fig, 3, save that itis so designed as to normally discharge the liquid which passes thewater actuated member upwardly through the boss 8 to a port opening 55directly into the outside chamber '56 of thethermostat b02157 throughwhich it passes upwardly to an opening 24 which communicates with thewater inlet 3 leading to the top coil 13 of the heating receptacle.After passing through said receptacle the water emerges from the loweroutlet opening a communicating with the lower reverse coil C of theheater, and enters the lower end of the inner thermostat chamber 58, andpasses upward through the latter to the pipe 5 which communicates withthe house supply system, lnthis case both'the pipe 57 which forms theouter wall of the thermostat box and the pipe 59 which divides said boxinto the outer and inner chambers 56 and 58 are made of iron, steel, orsome other suitablematerial having a very low coefficient of expension,and the inner wall of the pipe 59 is preferably coated with an elasticor semi elastic heat insulating enamel (such. for ex ample as thatcommonly used for metal electrical conduits), which will not be affectedby the action of hot water or by the slightexpansion and contraction ofthe tube. The opening between the upper end of the central. boss of thewater actuated member 6 and-the passage way 55 is provided with a checkvalve 9' which is pressed downward by a weak spring 10', but in the topclosed position of the water actuated member this check valve is heldslightly away from its seatby the upper end of the 11 stem. 60 whichpasses down through a stufi-. ing box in the lower'head of the cylinder2" and engages with a central boss on the gas valve piston 26. This stem60 is not directly secured to the piston member 6 but is provided with ashoulder 61 which, supports a valve seat 62and a leaf spring 63, theouter ends of which bear against the lower side of said piston. member,and serve to 'keep it normally. slightly raised away from the valve seat62 and against the seat of the boss 8', The lower end of the centralboss of this water actuated member is provided With ports 64, andanother port 65 leads from the lower end of the cylinder 2 13C to thelower end of the inner thermostat chamber 58. When the piston member 6is in the position shown in the figure the ports 6d are open, and allowthe water in the apparatus to pass, freely from the-inner the lattermember is provided with an upwardly extending fork 66 and an adjustablescrew 67 whereby it is connected to and actuated by a thermostaticcontrol mechanism. The thermostat member which I use in thisconstruction is of a novel character and consists of a series of wires,tapes, or very thin rods 68, 69, and 70 connected by top and bottomlevers 71 and 72 which are piv otally supported on knife edge screws 73and 74 mounted in caps secured to the ends of the tube 59. The upper endof the first, wire or rod 68 is likewise secured to the upper cap of thetube 59 and the lower end a of the wire 70 is secured to a plate 75which forms the end member of acorrugated diaphragm box 76 the interiorof'which is in free communication with the liquid in the innerthermostat chamber 58. It is readily seen that the expansions of thethree wires or bars 68, 69, and 70 will, when mounted in this manner becumulativein eflect, and that these three expansible members will bekept constantly under tension by the pressure of the liquid acting onthe elastic diaphragm box 76. The plate 75 is provided with a downwardlyprojecting button head which engages with the slotted fork 7-7 securedto the upper end of the stem 7 8 which passes'down through a stuflingbox in the top wall of a lateral extension 9 of the gas valve casing G.At the lower end this stem 78 is provided with a nut 79 which isprevented from rotation by a pin 80 engaging with a slot in the wall ofthe chamber 9.

This nut 7 9 bears against a thermostat lever 81 which is supported atits right hand end on adjustable screws 82 (one just back of, and onejust in front of sectional plane .of the drawing) and engages at'itsleft hand end with the screw 67 already described,

The operation of this mechanism is very similar to that of Figs. 1, 2,and 3. When no water is flowing through the heater the parts are inposition shown in the figure,

the water actuated member 6 being raised against the end of the boss 8',and the gas valve piston 26 being correspondingly raised to the highestposition to which it is permitted to move by the engagement of the cap27 with the adjacent shoulder of the gas valve casing G. The parts areheld in .this position by the joint action of the coil spring 47' andthe leaf springs 63. In this position the screw 67 is out of engagementwith the end of the thermostat lever 81, the parts being so adjustedthat no contact between these parts can take place at the very lowesttemperature to which the water in the thermostat chamber may fall. Whena flow of water is started through the apparatus by withdrawing theliquid from the house service pipe 5 the pressure on the lower side ofthe piston member 6' is reduced by such withdrawal of waterthrough theport and the piston member will im-.

mediately be depressed by the superior pressure of the inflowing wateron the top of it.

w sidethis movement being aided as in the previous construction by thewithdrawal of water from its under side-and will carry down with it thegas valve piston 26',-said movement continuing until the cap 27' hasbeen brought into contact with the upwardly projecting flange of the cap31. v The gas valve head 28 follows the downward movement of the gasvalve piston 26 untll the.

screw 67 engages with theend of the thermostat lever 81, whereupon thefurther motion of said gas valve 28 is arrested, and the gas valve portis opened by the further downward movement of the gas valve piston. Themaximum opening of this valve can be determined as before by theadjustment of the parts, but in this case it must be "such as to nearlycorrespond to the maximum movement of the gas valve under the extremeranges of temperature to which the water in the heater coils issubjected. The lifting of'the gas valve from its seat in the mannerabove describedallows fuel to flow from the pipe F through the ports 29and the gas valve port opening into the supply pipe H which leads to themain burners of the heater, where the gas is ignited by the usual pilotlight. As the temperature of the water flowing from the outlet of theheating receptacle through the inner thermostat chamber 58 rises, thewires or bars 68, 69, and 70 expand, and allow the head 75 to be moveddownward by the pressure p 82, and more conveniently by turning theforked head 77 and thereby moving the nut 79 up or down. The gas valve28 is thus closed, the fuel supply is shut oil from the main burners andthe temperature of the flowing water immediately begins to fall. Thiscontracts the parts 68, 69, and 70, raises the head 7 5 and with it thestem 7 8, the lever 81 and the gas valve 28, and admits a fresh supplyof fuel to the heating burners. As before, these opening and closingmovements of the gas valve will continue as the temperature ofthe'flowing water falls below and rises above the cut off point; but assoon as the fiow of water is stopped the pressure on the two sides ofthe piston member 6 will become equalized and the gas valve piston26will be raised to its initially described position thereby carrying thegas valve 28 "out of engagement with the thermostatically controlledmechanism and the gas valve will be then-kept seated both by its ownweight and by the pressure of the gas on its upper; side. The finalmovement of the water actuated member 6' to its closed position-as shownin Fig. 6 is elfected by the leaf spring 63, and in this position, asalready explained, means are provided for the free circulation of waterbetween the inner and outer thermostat chambers and through the heatingcoils which are connected at to and bottom of said outer and inner chamers. If the piss: ton member 6 should stick in its open position, andthereby prevent the spring 47 from returning the gas valve piston 26 toits upper position no damage could result to the heater, because undersuch circumstances the thermostatic mechanism would go on acting just asit did when the water was flowing, and shut off the gas whenever thetemperature of the liquid in the thermostat chamber had exceeded thepoint of thermostatic cut off. But in this case as before I insure thepositive return of the piston member 6' to itsclosedposition byproviding the automatically acting check valve 9 which, when the pistonis depressed, will immediately close against the upper end of the boss 8on the cessation of the flow of water, and will thus confine the body ofliquid in the heater between it and the now closed house service'pipe.The heating of this inclosed body of water will necessarily expand itand this expansion will pro duce a pressure on. the lower side of thepiston (the ports 64: now being closed by the seating of the valve 62)thus immediately raising it far enough to relieve the gas valve piston26. from all pressure of the stem 60 and. leaving said piston )free tobe returned to its top position by the tension of the strong compressionspring 47. lhis upward movement of the gas valve piston and of the stem60 will at the end open the check valve 9' and thereby equalize thepres-.

right angles to the axis of the vertically.

arranged thermostat chamber. This is the disposition of parts which iscommonly found in'present types of instantaneous hot water heaters. Theliquid from the water main is led to the apparatus through a pipe 1 thatenters the front end of the cylinder.

2 this cylinder containing the water actuated member 6 of the samegeneral construction as that shown in Figs. 3 and 6. A passage way 85leads from the port openings around the central boss 8 of the cylindermember to the lower end of an inner thermostat chamber 86. This chambercontains the negative tubular thermostat chamher element 87 which iscomposed of iron,

steel, Invar metal or similar'suitable material. The lower end of thiselement is closed by a perforated cap 88 through which the water flowsfrom the passage way 85 to the interior of the tube 87 and thence flowsupwardly tothe inlet 3 leading to the top coil of the heatingreceptacle. The upper end of the tube 87 is closed bya gravity actingcheck valve 89 which is provided with a' series of ports 90, which, whenthe check valve is raised will allow the water to flow from the chamber91 containing said check valve on into the chamber from which the water'inlet 3 leads. This check valve 89 is also provided with an upper head92, which, when the check valve is raised to permit the passage of waterto the inlet pipe 3?, is seated against the faces of the ports 93leading from the chamber above the check valve to the outer chamber 94cof the thermostat box. This outer chamber is formed by an inner tube 95of brass, copper or other similar material having a high coefficient ofexpansion, and constituting the positive element of the thermostatmember, and an outer tube 96 which may either be of the same material asthe inner tube or may be of iron. The inner tube 95 is secured at itslower end in the casing G? (which, in this case, contains both the wateractuated ele ment and the gas valve parts,) and is se cured at its upperend both to the cap 97 which connects the upper ends. of the inner andouter thermostat parts 95 31165.87, and also to the cap 98 whichcontains the check valve 89' and the ports 93. The upper end of the cap98 is machined and fitted within the head 99 and this is secured. inturn to the I terminal fitting 100 which closes the upper end ofthefouter tube 96, and contains a branch which leads to the houseservice pipe 5 The lower end of the tube 96, like the tube is secured inthe top part of the casingG, and a branch leads from the part of thecasing just below the end of the tube 96 to the water outlet 4 from thelower reverse heater coil. A second branch 101 leads from the lower endof the outer thermostat chamber 96 to a port 102 which opens into theleft hand end of the cylinder 2 The cap 88 which is secured to the lowerend of the inner thermostat member 87 is machined on its outer surfaceand neatly fitted in the lower end of the tube 95 which constitutes thepositive member of the thermostat, so that these two tubes may be freeto expand or contract differentially under theheating and coolinginfluence of the hot water passing up through the outer thermostatchamber and the cold water passing up through the central thermostatchamber. There will in the course of time be some leakage of waterthrough the sliding joint between the cap 88 and the tube 95, and thuswater will gradually fill the space between the tubes 87 and 95.Thisdoes no harm for the reason that the water in this space cannotcirculate, but forms simply a dead layer which acts in some respectslike an insulating sheet between the two tubular elements of thethermostat. The temperature of the inner element will always bepractically that of the cold infiowing water, while the temperature ofthe outer element will be that of the hot outflowing water. To the cap88 is secured a stem 103 which passes down through a stufiing box in thewall of the casing G and terminates in a knife edge opposite the shortarm of a thermostat lever 104. The long arm of this thermostat leverenters a fork 105 carrying an adjustable screw 106, and this fork issecured to the upper end of the stem 107 which passes down through astuffing box and is pivotally engaged at its lower end with the shortarm of the second thermostat lever 108. The lever 108 is of a bell crankform, and its long arm is pivotally connected to a fork 109 extendingout from'the back of the gas valve 28 This gas valve, like the onesshown in the constructions already described, is made in two partsbetween which the leather washer which forms the seat of'the valve isheld. In this construction the inner part is provided with a long hollowboss 110 which surrounds'a stud or stem 111 that is secured to the fronthead of the gas valve piston 26 Inter-posed between the end of the boss110 and the head of the stud 111 is a compression spring 112 whichserves to pull the two parts toward each other and normally keep thevalve 28 against its seat on the right hand end of the piston member 26the main burners of the heater. A fork 113 is secured to the front headof the gas valve piston 26 and a stem 114: leads from .this

fork through a stufling box in the front headof the water cylinder 2 andis secured in the central boss 7 of the piston member 6 A leather washer115 is secured to the end of this boss adjacent to the front cylinderhead and is held against said head at its outer end (when the piston isin position shown in the figure) by means of a light compression spring116, thereby sealing the opening around the stem 114 and preventing anyleakage of water at the point even when the stuffing box is quite loose.Two compression springs 117 and 118, one of which is interposed-betweenthe adjacent opposing ends of the gas valve piston 26 and the head ofthe'cylinder 2 and the other of which is interposed between the piston 6and the rear head of the cylinder 2 serve to keep said gas valve pistonmember and said water. actuated member normally in the position shown inthe figure.

The operation of this mechanism is readily understood from thedescription of the operations of the constructions already described.When no water is flowing the piston member 6 is held against the end ofthe boss '8 and in this position no water can v flow from the pipe 1into the apparatus. But as soon as a tap in the house service pipe 5 isopened water is withdrawn from the outer thermostat chamber 94, and alsowithdrawn from the back of the piston member through the .port 102. Thiswithdrawal of water sets up a difference in pressure between the twosides. of the piston member and the latter is moved to the left openingthe ports around the central bosses 7 and 8 and allowing water to flowthrough the passage way 85 to the central thermostat chamber 86 andthence through the 'port openings in the check valve 89 to the waterinlet 3 of the heater coils. The flow of water past this check valve 89lifts the latter and closes the port openings 93 thereby compelling allof the liquid which passes out through the pipe 5 to flow through theheater coils. The movement of the piston 6 to the left pulls the gasvalve piston 26 over against the shoulder 119, as shown in the detail ofFig. 8. The gas valve 28 will follow the motion of the gas -piston untilits the thermostat lever 104 has been brought in contact with the knifeedge on the stem-103, and willthen stop. If the temperature of the waterflowing through the outer thermostat chamber 94 is less than that forwhich the thermostat is set to cut ed the fuel'supply the main gas valveport between the gas valve 28 and its seat on the piston member 26 willbe opened allowing fuel to flow from the gas inlet pipe F to the gasoutlet pipe H and thence to the main burners of the heater where it isignited as before by the usual pilot or other means provided for thatpurpose. As the temperature of the flowing water rises the outerthermostat member 95 will expand raising the stem 103 and allowing thegas valve 28 to move toward its seat until it finally closes the maingas valve port and shuts off the fuel supply to the heating burners. Thepoint of final cut-off is determined by the adjustment of the screw 106,and is always effected by the contact of the flat disk portion of thegas valve 28 with the seat on the right hand end of the gas valve piston26 The inner coned part of this gas valve is provided only for thepurpose previously indicated, viz., to throttle the main gas valveopening prior to its complete closure, thereby more effectuallyregulating the flow of gas to the main burners of the heater than can bedone by the movement of a perfectly fiat gas valve. \Vhen the supply offuel to the main burners is cut off the temperature of the flowing waterat once begins to fall, and the outer thermostat member 95 begins tocorrespondingly contract, thus depressing the stem 103, raising'the longarm of the thermostat lever 10-1, and correspondingly moving the gasvalve 28 to the right away from its seat.

This'admits a fresh supply of fuel to the.

main burners. These opening and closing movements of the gas valve willcontinue as the temperature of the flowing water falls and rises belowand above the point of thermostatic cut off, the gas valve piston 26being held constantly in a, fixed position against the shoulder 119 bythe differential pressure set up by the flowing water on the two sidesof the piston member 6 As soon however as the flow of water stops thisdifferential pressure disappears, and the piston members 6 and 26 arereturned to their initial positions by the action of the springs 117 and118. In the initial position the gas valve is, as already explained,always closed, the range of movement being so propor tioned that in saidposition the thermostat;

leverlO is out of contact with the stem 103 at the very lowesttemperature that can be assumed by the water in the apparatus. When thewater flow stops the check valve 89,immediately returns to its seatthereby opening the ports 93 and allowing the water to pass freely fromthe outer thermostat chamber to theinlet 3 of the waterheater,

thus establishing a circulation for the liquid through the outerthermostat chamber and the heater coils, between the inlet and outletopenings 3 and 4 lhis return of the check valve to its seat alsoconfines the liquid in the heater between said check valve and the nowclosed house service pipe, and if the piston member 6 should stick inits opened position it will be immediately forced back to its seat byany further heating of said inclosed body of liquid in the manneralready described in the previous cases.

In Fig. 9 I have shown a slight modification of thermostat constructionwhich is illustrated in Fig. 7. In this case the cap 88 which is'securedto the lower end of the inner tubular thermostat member 87 is providedwith a drainage port 120 which leads from the space between the innerthermostat element 87 and the outer thermostat element 95 down throughthe stem 103 to the outside of the casing. This port will drain away anywater that leaks through the oint between the cap 88 and the tube 95 andthus keep the space between the inner and outer thermostat elementsalways open. In this way I preserve always an air insulating layerbetween these two elements thereby preventing very completely anyreciprocal heating or cooling eflect of the two streams of hot and coldwater passing through the outer and inner thermostat chambers 86 and 94;

In this construction shown in Figs. 10, 11, and 12 the water piston andwater actuated member contained therein are of precisely the sameconstruction as is illustrated in the construction of Fig. 7 This partof the apparatus therefore requires no ther description. In this casehowever the cold water which enters the passage way 85 does not fiowthrough any part of the chamber containing the thermostat member butpasses directly into a chamber 121 containing a check valve 89 andthence to a pipe 122 which leads to thecold Water inlet communicatingwith the top coil of the heater. After passing through the heater coilsthe water emerges from the outlet 1 and enters the chamber 123 whichcontains the ther: mostat member. The thermostat member which I use inthis case is of the liquid actuated type and-comprises two concentric.

the house supply system. A second port 129 leads from the outlet of thethermostat chamber to the port 121 in which the check valve 89 islocated, and'the said check valve end of a pipe 5 which communicateswith.

is provided with an upper head 92 which, when the check valve is raisedto allow the water to flow from the passage way 85 to the chamber 121,closes the port opening 129. A third port 102 leads from the thermostatchamber through a core piece in the passage way 85 into the left handend of the cylinder 2 The upper plate 126 of the thermostat member isconnected to a stem 130 which passes down through the lower plate 127and the part of the gas valve casing G which supports said plate andforms the lower wall of the thermostat chamber .123. This stemterminates in a knife edge which bears on the short arm of a thermostatlever 131, this thermostat lever being supported on two pivot pointscrews 132, one of which is just in front, and the other just behind thesectional plane of the drawing (see detail of plan view of thisthermostat lever in Fig. 11). The long arm of the thermostat leverenters a fork 133 secured to the upper face of the gas valve 28 andcarries in its upper cross-bar an adjustable screw 134. The gas valvewhich I use in this case is not provided with any conical surface suchas is shown in the constructions of Figs. 3, 6 and 7 but has a perfectlyfiat lower face which is adapted to engage with an upwardlv projectingring-seat on the top of the gas valve piston 26 This gas valve piston issomewhat different in form from any of those previously described,

being provided with a middle cross-wall having a central downwardlyprojecting fork 135 the lower cross-arm of which carries an adjustablescrew 136. The part of the gas valve casing G which forms the bearingfor this piston is closed at its lower end by a cap plate 137, a planview of which is-shown in Fig. 12. The cap plate is provided with twoupwardly projecting lugs 138 and 139 which are threaded at their upperends to receive pivot point screws between which is a mounted bell cranklever 140. The upper arm of this lever enters the fork 135 and engageswith the screw 136, and the lower arm enters this stirrup 141 andengages with a second adjustable screw 142 in the outer cross-arm ofthis stirrup. The inner end of said stirrup is secured to a stem 143which passes out through the side wall of the gas valve chamber andterminates in a fork 144 to which is secured the end of the stem 114which leads to the water actuated memberfi, and is connected thereto inthe same way as in the construction of Fig. 7. The middle plate of thegas valve piston is provided with three ports 29 at 120 degreeintervals, and the lower cap 137 is likewise provided with twocorresponding ports 145 and 146 and inter-' posed between the ribssurrounding these ports on the two parts ust mentioned are threecompression springsv 147 which serve to keep the piston 26 normallyelevated to the position shown in the figure in which the fork 144 is incontact with the adjacent face of the gas valve casing G, and the washer115 is also in contact with'the front wall of the water cylinder 2 j Thecap 137 is provided with a downwardly projecting boss which is threadedto receive the gas outlet pipe H which communicates with the mainburners, and the adjacent side wall of the gas valve chamber is threadedto receive one end of'a plug valve casing 148 interposed between thecasing and the gas inlet pipe F This plug valve casing is provided witha lateral branch connection 149 from which a tube 150 leads to the usualpilot light. It may be stated in this connection that a "similar plugvalve would ordinarily be used between the gas inlet pipe F and the gasvalve casing G in all of the constructions previously described; but assuch an arrangement is ordinarily used in all water heater constructionsof this type it is not specifically illustrated and described in eachcase. v r v The operation of this apparatus in regulating the supply ofgas to the main burners of the heater differs in no essential respectfrom that of the previously described mechanisms, although the flow ofwater through the apparatus follows a somewhat diiferent path, and therelative arrangement of parts is also different from those used in theconstructions of Figs. 3 to 9. The mechanism now being considered alsodiffers from those ioo part or element of the thermostat member issubjected to the'action of the cold inflowing water. The inner tube 125of the thermo stat may, if desired, be exposed to the action of the coldwaterin the chamber 85 by providing a port 151 and a stufiing box 152surrounding the lower end of the stem 130. As the use of this port 151is in this case optional it is indicated merely by dotted lines. If theport 151 is opened, and cold water is thus allowed to come in contactwith the inner tube 125 of the thermostat member the action of suchwater will be similar to that of the action of the inflowing water onthe thermostatic construction shown in Fig. 7, viz., it will reduce thetemperature of the positively acting member of the thermostatv ofthermostatic cut-ofi will be reached will not remain constant, but willbe automatically increased as the temperature of the cold inflowingwater is decreased. Hence in any given setting of the thermsotaticmechanism the temperature of the hot water supplied by the heater willbe automatically raised as the temperature ofthe water in the supplymain falls, and water will therefore be hotter in the winter than it isin summer. This is a result which is in any case very desirable ofattainment. On the other hand with the mechanisms illustrated in Figs.3, 6 and 9, in which the negative element alone of the thermostat isexposed to the action of the cold inflowing water-the positive elementbeing protected against such action either by a thermally insulatinglayer of enamel and intervening current of hot water or by a heatinsulating sheath of air-the effect of the fall in temperature of thecoldv inflowing water on the thermostatic control mechanism, is the sameas the effect of a rise in temperature of the hot out-flowing water onthat, mechanism. Hence with the mechanism of the constructions justreferred to a decrease in the temperature of the liquid supplied fromthe water main will resuit in the point of thermostatic cut off beingreached at a lower temperature of the outflowing water. In such casestherefore,

' with a given setting of the thermostat parts,

the water will be heated less in winter than it is in summer. This isalso a desirable result in some. cases, since it maintains the capacityof the heater at different times of the year at more nearly the samevalue.

Referring now briefly to the operation of the construction illustratedin Figs. 10, 11 and 12 .it will be noted that as soon as the water isturned on the water actuated piston member will be moved to the leftadmitting water to the chamber 85, and lifting the check valve 89-thereby closing the port opening 129. The water will flow past thecheck valve into the chamber 121 and pipe 122 to the inlet of the heatercoils, pass through these heater coils, emerge from the outlet 4 flowthrough the thermostat chamher 123, and out through the port 128 intothe house service pipe 5 The movement of the piston memberfi to the leftcarries with it the stem 11 1i and the stem. 143 connected thereto andoperates the bell crank lever 1&0 to draw down the piston member 26 Thedownward movement of this piston member is arrested by the engagement ofthe stirrup member 141 with the leather washer 153, said engagementserving to simultaneously seal the opening around the stem 143 againstthe escape of gas which flows into the lower part of the gas valvecasing. As the gas valve piston 26 moves downward the gas valve 28 willfollow it until the short arm of the thermostat lever 131 makes contactwith the knife edge on the end of the stem 130. If the temperature ofthe flowing water is less than that for which the mechanism may be setto out off the flow of gas, this contact will take place before the gasvalve has followed the piston. all the way down, and a port openingbetween the parts 26 and 28? will be left through which fuel will passfrom the gas supply pipe F through the ports 1 15 and 146 (Fig. 12) tothe gas outlet pipe H which leads to'the main burners, and fuel will beignited thereat by the flame of the pilot light constantly supplied withfuel through the connection 149 and pilot light tube 150. The flowingwater will be immediately raised in temperature by the heat of the mainburners and as it rises in. temperature it will expand the liquid in thethermostat and raisethestem 130, allowing the gas valve 28 -to movefurther downward, and finally seat itself on the gas valve piston headin the lowermost position of the latter. This will cut off the supply offuel to the main burners, and this point of final thermostatic cutoffmay be varied by adjusting the screw 134, access to which can beobtained by removing the cap provided for that purpose. When thetemperature of the flowing water falls the liquid in the thermostat willcontract, and'the thermostat member and stem 130 will be forced downwardby the pressure of the water in the thermostat chamber (this will occureven when the space within the inner tube is filled with water becausethe cross-sectional area of the outer tube 124: is greater than that ofthe inner tube 125), and this will depress the short latter s rin s alsoservin to raise the as valve piston 26 to its highest position, in whichposition the gas valve 28 is beyond the reach of any controlling actionexerted by the thermostat parts, and is kept closed by gravity. If thewater piston, or for that matter the gas valve piston, should stick inthe opened position, both of these parts will be forcedback to theirclosed positions by the expansion of the confined body of liquid in theheater (inclosed between the said check 89 and the now closed houseservice pipe), in. the same manner as previously described.

The construction shown in Fig. 13 differs from those already describedprincipally in having the gas valve head moved by the water actuatedelement, and in having the ,part which corresponds to the gas valvepiston controlled by the movement of the thermostatic mechanism. It alsodiffers from the previous constructions in certain details ofconstruction presently to be described. Liquid passes into the apparatusfrom the water main through the pipe 1* and enters a chamber 155, andthence to a pipe 122 which leads to an elbow connection 156 near the topof the heater shell. This elbow connection communicates with a secondchamber 157 containing a check valve 89* of the same generalconstruction as that illustrated in Fig. 10 and provided with a branchopening leading to the cold water inlet 3 of the top coil of the heatingreceptacle. The chamber 157 is also provided with port openings 129leading into the upper end of the thermostat chamber 123*. The checkvalve 89 is provided with a second head 92 which is adapted to close theport openings 129 and the check valve is normally held in the positionshown in the figurein which the opening between the chambers 156 and 157is closed and the ports 129 are openby a light compression spring 158.The chamber 155 .is further provided with a port 159 which leadsdownwardly into the right hand end of the chamber 2 whichcontains thewater actuated element, the latter being in this case a flexible metaldiaphragm 160, provided at its center with a metal ring or washer 161,which is faced with leather and normally held against the adjacent faceof an inwardly turned boss on the right hand head of the chamber 2 by acompression spring 118". A stem 114: is secured to the washer 161,passes through a stuffing boxand a cap 162 in the right hand head of thewater chamber 2, and is secured at its other end to the gas valve head28*. The space between the stuiling box and the cap 162 is provided witha cored passage way 163 which leads from this space to the outside ofthe casing G -which in this.case

also contains both the gas valve parts and the water actuated partssothat any water which leaks through the stufling box, when the leatherfaced washer 161. is withdrawn from the boss against which it rests, iscarried away to the outside of the apparatus. The water after passingthrough the heater coils emerges from the outlet 4 and enters a chamberwhich has two ports, one, 164 leading to the bottom of the thermostatchamber 123 and the other, 165, leading to the left hand end of thewater chamber 2 The thermostat chamber is formed in this case of asingle tube 166 which is secured at the bottom in the gas valve casing Gand at the top in the. casing of the chamber 157 and is closed at itsupper end-by a detachable cap 167 A branch connection 168 leads from theupper end of the thermostat chamber to the pipe 5 of thehouse supplysystem. The thermostat member which is placed in the tube 166 consistsin this case of a nest of iron, steel, or- Invar metal pipes 169 and 170which are brazed at both their top and bottom ends into hollow caps 171and 172. The first cap 171 is fitted neatly in the upper end of the tubesuitable liquid having a high coeflicient of expansion, or with parafiinor an eutectic alloy which melts at a temperature less than that atwhich the thermostat is desired to act, the volume of this inclosedspace being capable of adjustment by means of the screw 173. Thethermostat lever 175 is mounted on pivot point screws secured in lugsprojecting from the side of the gas valve casing G, and the long arm ofsaid lever passes through a fork or stirrup 176 on the back of themember which carries the gas valve seat 177. This gas valve seat issupported by an annular ring 178 of thin flexible leather or othersuitable gas tight material, the inper periphery of which is clampedbetween the gas valve seat 177 and the stirrup plate 176, the outerperiphery being clamped between the gas valve casing G and a ring 179which may be made in three or more segmental sections for convenience ofinsertion. The stirrup 176 carries an adjustable screw 180 which extendsthrough the plate 181 closing the right hand endof the gas valve casingG and is covered by a cap 182. A compression spring 183 is interposedbetween the stirrup 176 and the cap 181 and serves to keep said seat 177normally closed against the gas valve head 28*. The long end of thethermostat lever is extended down motion of the thermostat lever underthe action oi the tension spring 184.

The operation of the mechanism shown in the last described figure willbe readily understood, since it is,-in all general respects, the same asthat of the various other forms of mechanism illustrated in the earlierfigures. When no water is flowing through the apparatus the pressures onthe two sides of the diaphragm 160 will be substantially the same, andthe diaphragm is held in the position shown in the figure by the spring118", which, in conjunction with the spring 183, holds. the gas valvehead and its seat 1n closed relation with respect to each other, andprevents any fuel flowing from the right hand side of the gas valvecasing G to the left hand side; the screw 186 being so adjusted that inthis position of the parts the thermostat lever is prevented fromengaging with the screw 180. When a flow of water is established-as byopening the tap in the house service pipe 5-a difference in pressures isestablished on the two sides of the'diaphragm member 160 (which areexposed respectively to the pressure of the water in the inlet ch: :nber155 and the out- .let passage 164) by the resistance to the flow of theliquid through the heater coils. 'Un der this difference in pressure thedia phragm member willbe moved to the left until the washer on the backof the gas valve head 28* comes into engagement with the cap 162,thereby both arresting the motion of the water actuated parts andsealing the stem opening in the cap 162 against any escape of gas. Theseat ring 177 Wlll follow the motion of the gas valve headunder theaction of the spring 183-until the end of the screw 180 comes in contactwith the thermostat lever 175, and the motion of the seat ring will thenbe arrested by the superior tension of the spring 184. If thetemperature of the flowing water is less than that for which thethermostat mechanism is set to cut off the fuel supplyas determined bythe adjustment of the screw 180the motion of the seat ring will bearrested before it has followed the gas valve head to the extreme lefthand position, and a port opening will be left between. said seat andhead through which fuel will flow from the gas inlet pipe F to thegasoutlet pipe H which communicates with the main burners. The fuel thussupplied to these burners will be ignited by the usual pilot light, andthe heat generated will immediately begin to raise the temperature ofthe flowing Water, and this in turn will further expand the liquid inthe thermostat tubes and thereby depressthe knife edge on the diaphragmbox 17 4. This will move the long arm of the thermostat to the leftunder the tension of the spring 184, and this in turn will allow theseat ring to be moved still-further toward the gas valve head by thespring 183, until the gas valve port is ultimately closed thus shuttingoff the fuel supply to the heating burners. The temperature of theflowing water will then begin to fall and the resultant contraction ofthe liquid in the thermostat member will allow the long arm of thethermostat lever 175 to be moved to the right by the spring 184, andcarry with it the seat ring 17 7 thus a once more opening the main gasvalve port and allowing a fresh supply of fuel to pass therethrough, Thecontrolling action of the ring 17 7 and carrying thelatter out of the;

range of action of the thermostatic mechanism. In this constructionthere is very small chance of any of the parts sticking in their openedposition, but if this should oc* our the diaphragm member 160 will bepositively returned to" its right hand position by the automatic closingof the check valve 1 89 and the subsequent expansion of the thenconfined body of liquid in the heating receptacle. The closing of thischeck valve on the cessation of the flow also opens the ports 129* andallows the water in the apparatus to circulate freely through thethermostat chamber and the heatervcoils, between the inlet and theoutlet openings 3 and 4 In the last described construction I have notmade use of that feature of my invention which relates to the exposureof the negative and positive elements of the thermostat member to theaction of the inflowing and of the outfiowing streams of water, but itwill now be obvious to those skilled in the art that in this case as inthe others already described, the thermostat member and its surroundingparts could be so modified as to embody these features in myimprovements whenever it is desired to do so. 4

As has already been indicated certain features of my improvements arealso applicable in connection with storage tank heaters. In this casethe water actuated element is not directly effected by the inflow oroutflow of water to or from the apparatus, but is so constructed andarranged as to be affected only by the fillin or emptying of the system.not only necessary to subject one side of the In order to e ect thisresult it is water actuated memberthat side which corresponds, in theinstantaneous type of heater, to the inlet side-to the pressure of thewater in. the tank or some other conof said chamber led directly intothe passage way 164. \V'hen so placed the right hand side of thediaphragm 160 would be exposed,

to the full water pressure in the apparatus, and, in consequence ofthis, the valve head 28* would be held in the open position as long asthe heater was filled with liquid. The-thermostat mechanism would thenoperate to open and close the gas valve as the temperature of the liquidin the tank fell below or rose above the point for which thethermostatic cut ofi may be set to act. hen the apparatus was emptied ofwater the diaphragm member 160 would be restored to the positiop shownin Fi 13 by the spring 118*, thus carrying the va ve head 28*, .and theseat cooperating therewith, out of range of action of the thermostaticmechanism. This will prevent any fuel being admitted to the main burnersof the heater when there was no liquid in the apparatus.

In Fig. 14 I have illustrated another construction of parts moreespecially designed for use in a storage tank heater. In this figure 190indicates the head of the tank. The frame of the apparatus is attachedin any suitable manner to the head as by screw-- ing or bolting itagainst a plate 191, which is riveted to said head. The lower part ofthis frame is bored to form a piston chamber 192, which opens directlyintothe tank, and contains a packed piston 193', which, when theapparatus is filled with liquid, is held tightly against the frontshouldered end of the piston chamber. In this position leakage past thepiston is prevented not only by the packing rings, but also by aleatherwasher 194 which is interposed between the front end of thepiston member 193 and the shoulder ring against which it is tightlypressed by the water pressure. The piston is provided with forwardlyextending lugs, carrying at. their front ends a pin which engages withthe vertical arm of a bell crank lever 195, and the horizontal arm ofthis bell crank; lever is engaged. in turn with a pin carried by adownwardly extending lug on the lower head of the gas valve piston 26',

somewhat similar in constructionto the one shown in Fig. 10. The upperend of this gas valve piston is formed with a seat with which the gasvalve 28 is adapted to engage, and it is provided with lateral ports 29which lead from the interior of the pistonto an encircling chamber 30that communicates with the gas outlet pipe H lead ing to the mainburners of the heater. The gas is led into the upper part of the chambercontaining the gas valve through the pipe F 5 and the gas-valve itselfis carried by a leather diaphragm178 This diaphragm is clamped inposition by means of a shallow recessed cap plate 196, and a small, portopening 197 leads from the gas chamber be:

low the diaphragm to -a space between'this recessed cap plate and thetop side of said diaphragm. This port opening is opened and closed by apoppet valve 198 carried on a stem which projects through a stufiing boxin the cap plate 196 and terminates in a recessed head 199, the valvebeing held normally against its seat by means of a spring 200 interposedbetween said head and the said cap plate. A second port 201 leads fromthe space above the diaphragm to the exterior of the apparatus, thisport being opened andclosed by means of a valve 202 which is heldagainst its seat by a. spring 208. A thermostat member of the usualcomposite construction-comprising an outer positive tubular member 204of copper, brass, or some highly expansible metal, and an inner negativemember 205 of iron, steel, porcelain or similar material having a lowcoefiicientof expansionis secured to the frame of the apparatus andprojects horizontally through the wall of the tank so as to be exposedfor the greater part of its length to the liquid .in said tank. The endof the inner negative member 205 terminates ina knife edge which bearsagainst the short arm of the thermostat lever 206, the long armof thisthermostat lever carrying an adjustable screw 207 which is adapted toengage with the head 199. The long arm of this lever is'also perforatedto receive the stem 208 of the valve 201, and the upper end I of thisstem is threaded to receive an adjustable thumb nut 209 which is adaptedto engage with the upper side of the thermostat lever 206. This lever isheld in engagement with the knife edge, and causes it to follow themovements of the latter by means of the tension spring 210 which isconsiderably stronger than the spring 200.

The operation of the water actuated member in carrying-the gas valvepiston 26 into and out of operative position is substantially the sameas the-operation of the correspond ing parts in the mechanismspreviously described. That is to say, when the apparatus is filled withliquid the pressure of said liquid on the back of the piston forces1tforward, and depresses the gas valve piston 26 to the position shownin the figure. But the operation ofthe thermostat control mechanism inopening and closing the gas valve in this position of the gas valvepiston is somewhat different from any of the thermostatic controlmechanisms already described in that the thermostat lever does notjected to the act directly on the gas valve head 28", but acts only tocontrol the relative pressures of gas on the two sides of the gas valvediaphragm 178 and these differences in pressure so controlled are usedto directly move the gas valve head, and. thus turn on or turn off thefuel to the main burners of the heater. This is accomplished in thefollowing manner: When the temperature of the water in the tank is lessthan that desired the long arm of thenthermostat lever 206 is raisedbythe pressure of the knife edge on the negative thermostat member 205-tosuch a height that the screw 207 is out ofengagement with the head 199,and the valve 202 is raised from its seat by the engagement of thethermostat lever 206 with the thumb nut 209. When the valve 202, and theport 201 controlled thereby, is open the upper side of the diaphragm 178 is subjected only to the pressure of the atmosphere, while the lowerside of the said diaphragm is subpressure of the gas in the fuel supplypipe H. The diaphragm 17 8 is made of such a size that the gas pressureon the lower side thereof is sufiicient to raise the valve 28 from itsseat, thus allowing fuel to flow to the gas inlet pipe H and thence onto the main burners, where it is ignited by the usual pilot light,constantly supplied with gas through an independent pipe not shown inthe drawing. The gas valve will remain open and fuel will continue toflow past it until the temperature of the water in the tank has beenraised to such a point that the expansion of the positive thermostatmember 204 has retracted the knife edge on the negative member 205sufiiciently to allow the thermostat lever 206 to be depressed to such-aposition that the valve 202 will be closed by the pressure of the spring203, and the valve 198 will be opened by the engagement of the screw 207with the head 199. When this occurs gas will flow into the chamber abovethe J diaphragm through the ort 197, andboth sides of the diaphragm 1 8being now subjected to-the same pressure, the gas valve 28 will beclosed against its seat ting off any further flow of fuel to the gassupply pipe I. As the temperature of the liquid in the tank falls-byreason either of gradual loss of heat by radiation or by reason of awithdrawal of hot water and consequent inflow of cold water-thethermostat member will contract thus lifting the long arm of thethermostat lever 206 until the valve-198-has closed and the valve 202has opened again. When the last described action occurs the pressure onthe top side of the diaphragm 17 8 is once more relieved, and the maingas valve is again opened allowing a fresh supply of fuel to flow to theheater burners. It has been found in practice that a four-inch die bygravity thus shutopening and clos phragm is sufficiently large tooperate the gas valve, and diaphragm need be only of sufiicient depth toallow for about a one-eighth inch movement of the gas valve in openingand closing, the volume of gas discharged through the port 201 at eachopening movement of the main gas valve will'be less than. two cubicinches. In storage tank heaters the number of the opening and closingmovements rarely exceeds one hundred in each twenty-four hours, and isas a rule much less than this. The total volume of gas discharged in theair is therefore less than one hundred cubic inchesonly aboutonetwentieth of a cubic foot-in an entire day;

and this is a quantity that is absolutely negligible and absolutelyindistinguishable.

the chimney vflue or into the'casing of the heater coils, or 'intoeither the main outlet pipe H or the pilot light tubein the man? nerdescribed in my co-pending application of even date Ser. No. 744,198. Assoon as the heating apparatus is filled with water the opening andclosing gas valve will continue as the temperature of the water in thetank falls below or rises above the points at may be set to act on thevalves 198 and 202, these points being adjusted by means of the screw207 and the thumb nut 209. But when the water is drawn entirely out ofthe heater the pressure on the piston 193 will be removed, and the gasvalve piston 28 will then be raised by the action of the compressionspring 211, and will carry up with it the gas valve head 28 until theupper side of the latter has been brought against the cap 196 therebylocking the gas valve port, no matter what may be the position of thethermostat control parts.

since the chamber above this movements of themain which the thermostatThe advantage of using this pneumatic thermostatic control-in place ofsuch con- 13is that the main gas valve is either fully opened .orentirely closed, and that these 'ng movements take place with a snap.closing off or the gradual letting on of the gas to the main burnerswhen the temperature of the water in the tank is near that for which thecontrol mechanism may be set to act. In storage tank heating systemssuch gradual turning on or off of the fuel supply This avoids the.gradual movement of the thermostatic control parts,

is for that reason, more sluggish in one case than in the other. Itwill'however be now apparent tothose skilledin the :rt' that I may, ifdesired, use a pneumatic snap controlthermostatically operated-similarto that illustrated in Fig. 14 in place of the direct thermostaticcontrols illustrated in the constructions of Figs. 1 to 13. Such anapplication of a pneumatic snap thermostatic control to theinstantaneous type of hot water heater is shown and described in myapplication Ser. No. 699,816.

- In Fig. 15 I illustrate another form of constructionembodying certainfeatures of my present improvements also particularly designed for usein connection with a storage tank heating system. In this construction190 indicates the wall of the tank, the frame of the apparatus beingsecured thereto in the same manner as indicated in Fig. 14. In this casethe water actuated member of the apparatus consists of a corrugatedmetal diaphragm 212 which is exposed on its right'hand side to thedirect pressure of the water in the tank. This pressure normally forcesthis member forward into the position shown in the figure against thepressure of the spring 213, bringing the gas valve piston 26 and themain gas valve 28 cooperating therewith into the position shown. Thethermostatic control system which I use in this case is of the magneticsnap type more fully described and illustrated in my copendingapplication Ser. No. 744,198. The

thermostatic part itself is'of the same type of construction as thatshown in ig. l4 and comprises an outer positive member 204 and an innernegative member205, the

latter terminating in a knife edge which,

bears against the short arm of a thermostat lever 206. The long arm ofsaid lever carries an adjustable screw 214 which bears in turn againstthe short arm of a second thermostat lever 215, the long arm of thelatter carrying a horse shoe shaped electric magnet 216, the plane ofwhich is at right angles to the sectional plane of the drawing. Thepoles of this electro magnet-one of which is behind, the other of whichis in front of the plane of the drawingare be tween two soft ironbararmatures 217 and 218 which are adjustably secured to the stem 219 ofthe main gas valve 28 It is provided withtwo collars 219 and 220, one ofwhich is adapted to directly engage the left hand side of the gas valve28, and the other of. which engages the right hand side of said valvethrough the medium of a compression spring 221 interposed between thecollar 220 and said gas valve. An anti-friction roller 222 may, ifdesired, be placed on the inner perforated head of the gas valve piston26 to support the right hand end of the stem 219. Adjustable stops 223and 224 are secured to the thermostat lever 215 to limit the motion ofsaid lever and the magnet 216 carried thereby in both directions; andcompression springs 225 and 226 are arranged to act on the twothermostat levers 215 and 206 respectively, the latter spring beingstrong enough to overcome the tension of the former when the two actagainst each other.

The operation of this thermostatic control mechanism is as follows: Whenthe temperature of the water in the tank is above that for which thethermostat is set to act the retraction of the knife edge on thenegative member 205 allows the spring 226 to bring the screw 214 intoengagement with the second thermostat lever 215 and move it and themagnet 216 to the right as far as the adjustable step 224 will allow.The stop 224 and the armatures 217 and 218 are so adjusted that in thisposition the poles ofthe magnet 216 are'nearer to the armature 218 thanthey are to the armature 217, and the superior attraction of said polesto the right hand armature will thereupon move the stem 219 and partsconnected thereto the left thus pulling the gas valve 28 against itsseat. and preventing any flow of fuel past said valve from the gas inletpipe F to the gas outlet pipe H As the temperature of the water in thetank falls the contraction of the thermostat member will force down thethermostat lever 206, withdraw the screw 214 out of engagement with thelever 215 and allow the latter to be moved to the left by the spring 225until the step 223 comes into engagement with its limiting boss. In thisposition of the lever 225 and the magnet 216 the poles of the latter arebrought closer to the left hand armature 217' than they are to the righthand one, and the former armature will be moved toward the magnet polescarrying with it the stem 219 and the gas valve 28 and thus open themain gas valve port and allow fuel to flow through it to the pipe H andthence onto the main burners of the heater where it will be ignited bythe usual pilot light. The gas valve will remain open until thetemperature of the liquid in the tank has been raised to such a pointthat the screw 214 is once more brought into engagement with the lever215 and moves the latter to the initial position

